This chapter explores Krashen’s Input Hypothesis, a foundational theory in second language acquisition (SLA), which posits that learners acquire language subconsciously when exposed to comprehensible input slightly beyond their current proficiency level (i+1). The hypothesis emphasizes the importance of meaningful, context-rich input over explicit instruction, suggesting that language acquisition occurs naturally through listening and reading. The chapter discusses practical applications of the hypothesis in classroom teaching, such as creating language-rich environments, using authentic materials, and employing scaffolding techniques to ensure comprehension. It also addresses criticisms of the hypothesis, including its perceived neglect of output and interaction, and its methodological challenges in testing. The chapter highlights the need for tailored input strategies based on learners’ age, proficiency levels, and learning goals, advocating for a balanced approach that integrates input with opportunities for meaningful output and guided practice. By combining comprehensible input with interactive and authentic learning experiences, educators can foster linguistic proficiency, cultural awareness, and intrinsic motivation in learners. The chapter concludes with recommendations for future research and innovative teaching practices to enhance the application of the Input Hypothesis in diverse language learning contexts.